Boats which are propelled by propulsion systems, such as stern drive systems, commonly have an aperture in the transom through which extends a part of the stern drive system to enable transmission of power from an engine within the boat hull to a propulsion unit positioned rearwardly of the transom. Mounting of the stern drive system through the transom has required a seal to prevent entry of water through the aperture into the boat hull. Various arrangements have been employed in the past for providing a seal between the stern drive and the boat transom to prevent entry of water into the interior of the boat. Unfortunately, it is believed that each of such prior sealing arrangements may be somewhat vulnerable to single failures, that is, if the seal develops a single rupture, the boat could sink. Further, typical seals have involved various parts, such as trims, castings, and screws, and have been relatively burdensome to assemble and to remove when removal is required, as for instance, when removing the stern drive system for repair or replacement.
Thus, it is desirable to provide a seal having structural redundancies that provide independent dual sealing, that is, a seal that would require separate failures of each of the structures that respectively provide independent sealing before the overall transom seal would be compromised. It is further desirable to provide a seal that may be readily assembled during manufacturing operations and that further may be easily removable during servicing or maintenance operations.